Power control unit

ABSTRACT

A tracked vehicle has a power control apparatus for controlling charging and discharging of a plurality of storage devices. A voltage measuring device measures voltages of the respective storage devices, and a current measuring device measures currents flowing through the respective storage devices. A status detecting device detects the operating status of each storage device based on values measured by the voltage and current measuring devices; and a charging/discharging controlling device controls currents, voltages, or power according to the operating status of each storage device detected by the status detecting device, to charge or discharge the storage devices.

This application is a continuation of U.S. patent application Ser. No.11/228,195, filed on Sep. 19, 2005, now issued as U.S. Pat. No.7,075,306, which in turn claims priority of U.S. patent application Ser.No. 10/751,905, filed Jan. 7, 2004, now abandoned, both of which arehereby incorporated by reference as if set forth herein in theirentirety.

BACKGROUND OF THE INVENTION

This invention relates to power control apparatus which controlscharging and discharging of a power-generating or rechargeable powersupply such as a fuel cell, lithium secondary cell, nickel metal-hydridebattery, lead-acid battery, and electric double layer capacitor.

When a plurality of storage means such as batteries are connected inparallel, series, or both or when a plurality of storage means ofdifferent types are connected in parallel, series, or both, currentsflowing through the storage means are dependent upon voltages andimpedances of the storage means.

Therefore, when the storage means which are connected in parallel,series, or both are charged or discharged at a time, the current orvoltage value of a certain storage means may exceed a permissible value.

To solve such a fault, prior arts have employed a method of controllingcharging or discharging of the storage means with the minimum ofcurrents that can flow through the storage means instead of charging ordischarging with a total of currents that flow through allparallel-connected storage means (n pieces).

Japanese Application Patent Laid-Open Publication No. 2002-142353discloses a method of disconnecting a faulty storage means when itscurrent or voltage goes above a permissible value.

FIG. 9 shows a conventional method of controlling charging anddischarging storage means. In FIG. 9, two or more sets 7 ofseries-connected batteries 1 are connected in parallel. Each set 7 ofseries-connected batteries 1 further comprises a means 9 for detecting afault such as a micro short-circuit of each battery 1, a current bypasscircuit 3 which comprises a current control means (switch) 4 and aresistor 5 and is connected to the battery set 7 in parallel with theset 7, and a fuse 6 which is connected in series to the bypass circuit 3and the battery set 1 to electrically shut off the circuit when anovercurrent takes place.

When faults such as a micro short-circuit occur in a battery 1, it isdetected by its voltmeter 2. The fault detecting means 9 receives asignal from the voltmeter 2 and closes the switch 4 to flow a largecurrent through the current bypass circuit 3 which is connected inparallel to the faulty battery 1. This large current blows off the fuse6. With this, the faulty battery is disconnected from the othernon-faulty battery sets.

Japanese Application Patent Laid-Open Publication No. 2001-185228discloses a system comprising two or more parallel-connected batterymodules each of which has two or more secondary batteries connected inseries. A current detecting circuit and a switch are connected in seriesto each battery module.

When one of the current detecting circuits detects an abnormal currentvalue or direction, a control unit opens a switch of the battery modulecontaining a faulty battery to disconnect the faulty battery module fromthe other non-faulty battery modules.

Japanese Application Patent Laid-Open Publication No. 08-88944 disclosesa system which connects a plurality of cells each of which is asecondary battery or a plurality of battery modules each of whichcomprises two or more secondary batteries in series, parallel, or both.This system detects the voltage and the current of each cell or moduleand calculates the quantity of charge.

The system selectively charges cells or modules according to the resultof calculation.

SUMMARY OF THE INVENTION

However, the prior arts disclosed by Patent Documents 1 and 2 cannotcharge or discharge currents for “n” batteries in a system having “n”sets of parallel-connected storage means each of which contains aplurality of series-connected batteries and cannot increase theinput/output (current) further.

This is because a current by a single battery is charged to ordischarged from “n” sets of parallel-connected storage means in order toavoid charging or discharging by an over-current assuming that theperformances of the batteries are different.

A time period required to charge or discharge “n” sets ofparallel-connected storage means by a single battery is longer by “n”times than that required to charge or discharge one battery by a singlebattery.

Therefore, the conventional methods will be available to apparatus thatdo not require quick charging and apparatus that have a smallerdischarging current than the capacity of the storage means and do notmind the charging/discharging time.

However, power equipment for vehicles, emergency power equipment, or newrechargeable power supply apparatus for home use require quick chargingand less weight. In other words, it is very important for such equipmentto reduce the capacity relative to the discharging current. However, itis beyond the ability of the conventional technologies.

The technologies of Patent Documents 1 and 2 are designed to disconnectthe storage means from the power control circuit only after the storagemeans has a trouble instead of controlling charging and discharging ofthe storage means to prevent troubles from occurring in the storagemeans. It is possible to make the service life of the storage meanslonger by controlling charging and discharging of the storage means tosuppress occurrence of troubles.

Therefore, it has been hoped that a power control apparatus beactualized that can control charging and discharging of storage means tosuppress occurrence of troubles while enabling quick charging andreduction of the capacity relative to the discharging current.

On the other hand, the technology in Patent Document 3 controls tocharge storage means according to the charging quantity of respectivebatteries to suppress the occurrence of a trouble in the storage means.

However, the technology in Patent Document 3 considers neither quickcharging nor reduction of the capacity relative to the dischargingcurrent and cannot accomplish these. Further, this technology employs aconfiguration in which each battery is equipped with a current controlcircuit and a current control element. This makes the configuration ofthe power control apparatus complicated and heavy. This technology isfar from weight reduction.

Accordingly, an object of the present invention is to provide a powercontrol apparatus that can control charging and discharging of storagemeans to suppress the occurrence of a trouble in the storage means whileaccomplishing quick charging and reduction of battery capacitiesrelative to discharging currents.

To accomplish the above purpose, this invention is configured asfollows:

(1) A power control apparatus for controlling charging and dischargingof a plurality of storage means, comprising

voltage measuring means for measuring voltages of said storage meansrespectively,

current measuring means for measuring currents flowing through saidstorage means respectively,

a status detecting means for detecting the operating status of eachstorage means from values measured by said voltage measuring means andsaid current measuring means, and

a charging/discharging controlling means for controlling currents,voltages, or power according to the operating status of each storagemeans detected by said status detecting means to charge or dischargesaid storage means.

(2) In (1) preferably, the status detecting means preferably calculatesthe internal impedance or open circuit voltage of each storage means andthe charging/discharging controlling means controls charging/dischargingcurrents, voltages, or power of said storage means according toimpedances or open circuit voltages thereof.

(3) In (1) preferably, said status detecting means calculates theinternal impedance or open circuit voltage of each storage means and

said charging/discharging controlling means calculates the permissiblecharging or discharging current value of each storage means from itsinternal impedance, open circuit voltage, preset maximum permissiblevoltage and minimum permissible voltage, calculates the sum of allcurrents flowing through said storage means to suppress a current overthe calculated permissible charging or discharging current from flowinginto or out of each of said storage means and controls the charging ordischarging current to make the total current below the calculated totalcurrent value.

(4) In (1) preferably, said status detecting means calculates thecharging status of each storage means and determines the maximum orminimum of the calculated charging states, and said charging/dischargingcontrolling means controls the charging current, voltage, or power bythe maximum charging status value and controls the discharging current,voltage, or power by the minimum charging status value.

(5) In (1) preferably, said power control apparatus further comprises aswitch means which selectively breaks or makes a connection between saidcharging/discharging controlling means and any storage means and saidcharging/discharging controlling means checks the on/off status of saidswitch means and controls the current, voltage or power according to thedetected on/off status of said switch means and the running status ofeach storage means to discharge or charge the storage means.

(6) In (5) preferably, said status detecting means calculates theinternal impedance or open circuit voltage of each storage means andsaid charging/discharging controlling means controlscharging/discharging currents, voltages, or power of said storage meansaccording to the impedances or open circuit voltages thereof.

(7) In (5) preferably, said status detecting means calculates thecharging status of each storage means and determines the maximum orminimum of the calculated charging states, and said charging/dischargingcontrolling means controls the charging current, voltage, or power bythe maximum charging status value and controls the discharging current,voltage, or power by the minimum charging status value.

(8) In (1) to (7) preferably, said power control apparatus furthercomprises a load and a means selected from a group of a commercial powersupply, a solar energy generator, a micro gas turbine generator and afuel cell to supply power to said load, wherein said power controlapparatus supplies power to said load or said commercial power supplyand uses power from said commercial power supply, a solar energygenerator, a micro gas turbine generator or a fuel cell as a chargingpower.

(9) In (1) to (7) preferably, said storage means supply power to anelectric motor which drives vehicle wheels and are charged by power fromthe outside of a vehicle or power from said electric motor when saidmotor is used as a power generator.

(10) In (1) to (7) preferably, said storage means supply power to anelectric motor which drives vehicle wheels and are charged by powergenerated by a dynamo-electric generator which is driven by an internalcombustion engine on a vehicle or power from said electric motor whensaid motor is used as a power generator.

(11) A power control apparatus for controlling charging of a pluralityof storage means comprising voltage measuring means for measuringvoltages of said storage means respectively, current measuring means formeasuring currents flowing through said storage means respectively, astatus detecting means for respectively calculating the internalimpedances and open circuit voltages of said storage means from valuesmeasured by said voltage and current measuring means, and a chargingcurrent controlling means calculates a permissible charging currentvalue of each storage means from its internal impedance or open circuitvoltage and a preset maximum permissible charging voltage which aredetected by said status detecting means calculates the sum of allcurrents flowing through said storage means to suppress a current overthe calculated current from flowing into said storage means, andcontrols the charging current to make the current below the calculatedtotal current value.

(12) A power control apparatus for controlling discharging of aplurality of storage means comprising voltage measuring means formeasuring voltages of said storage means respectively, current measuringmeans for measuring currents flowing through said storage meansrespectively, a status detecting means for respectively calculating theinternal impedances and open circuit voltages of said storage means fromvalues measured by said voltage and current measuring means, and adischarging current controlling means calculates a permissibledischarging current value of each storage means from its internalimpedance or open circuit voltage and a preset maximum permissibledischarging voltage which are detected by said status detecting meanscalculates the sum of all currents flowing through said storage means tosuppress a current over the calculated current from flowing from saidstorage means, and controls the discharging current to make the currentbelow the calculated total discharging current value.

In summary, the present invention can provide a power control apparatusthat can control charging and discharging of storage means to suppressthe occurrence of a trouble in the storage means while accomplishingquick charging and reduction of battery capacities relative todischarging currents.

This invention is applied to an energy management system of variousstorage means such as power generating elements such as fuel cells,lithium secondary cell, nickel metal-hydride battery, lead-acid battery,and electric double layer capacitor and systems using thereof such aspower supply equipment, distributed power storage equipment, electriccars and vehicles, and tracked vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given hereinafter and from the accompanying drawings of thepreferred embodiment of the present invention, which, however, shouldnot be taken to be limitative to the invention, but are for explanationand understanding only.

In the drawings:

FIG. 1 is a schematic diagram of a power control apparatus which is thefirst embodiment of the invention.

FIG. 2 is a functional block diagram of the inside of acharging/discharging controlling means in accordance with the embodimentof FIG. 1.

FIG. 3 is a graph for explaining an example of process that the statusdetecting means executes.

FIG. 4 is a schematic diagram of a power control apparatus which is thesecond embodiment of the invention.

FIG. 5 is a schematic diagram of a power control apparatus which is thethird embodiment of the invention.

FIG. 6 is a schematic diagram of a power control apparatus which is thefourth embodiment of the invention.

FIG. 7 is a schematic diagram of a power control apparatus which is thefifth embodiment of the invention.

FIG. 8 is a schematic diagram of a power control apparatus which is thesixth embodiment of the invention.

FIG. 9 shows a schematic diagram of a conventional power storage controlapparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described below withreference to the accompanying drawings, in which like reference numeralsrepresent the same or similar elements.

FIG. 1 is a schematic diagram of a power control apparatus which is thefirst embodiment of the invention. This embodiment is an example ofapplying the present invention to a power supply charging/dischargingcontrolling means.

In FIG. 1, means 101 a and 101 b are power storage means. A means 101 bis a voltage measuring means. Means 103 a and 103 b are currentmeasuring means. A means 104 is a status detecting means and a means 105is a charging/discharging controlling means.

A current measuring means 103 a is connected in series to a storagemeans 101 a and a current measuring means 103 b is connected in seriesto a storage means 101 b. The series set of the current measuring means103 a and the storage means 101 a is connected in parallel with theother series set of the current measuring means 103 b and the storagemeans 101 b.

A voltage measuring means 102 is connected in parallel with theseparallel sets of the current measuring means 103 and the storage means101. Further, a charging/discharging controlling means 105 is alsoconnected in parallel with the storage means 101 and current measuringmeans 103. This charging/discharging controlling means 105 is connectedto a power supply such as a commercial power supply, a power generatorand a fuel cell and to a load such as an electronic apparatus (which arenot shown in the drawing).

The status detecting means 104 receives a measured voltage value fromthe voltage measuring means 102 and measured current values from thecurrent measuring means 103 a and 103 b, calculates the resistance andthe voltage of each storage means, and sends the result to thecharging/discharging controlling means 105.

The charging/discharging controlling means 105 performs operations (tobe described below) on the status values (resistances, voltages, and soon) sent from the status detecting means 104 and controls the chargingand discharging currents of the storage means 101 a and 101 b by theresult.

In this case, it is possible to provide a temperature measuring means, apressure measuring means, or both (not shown in the drawing) to measurethe status of each storage means 101.

The power storage means 101 a and 101 b are power-generating orrechargeable power storage means such as a fuel cell, lithium secondarycell, nickel metal-hydride battery, lead-acid battery, and electricdouble layer capacitor. These storage means are used singly or plurallyin series or in parallel.

The voltage measuring means 102 comprises some electronic parts such asvoltage-dividing resistors, operational amplifiers, and A/D convertersand measure the voltage of each storage means. Although this embodimenthas the voltage measuring means 102 and the status detecting means 104separately, part or the whole of the voltage measuring means 102 can bebuilt in the status detecting means 104.

Each of the current measuring means 103 a and 103 b consists of a HallCT or shunt type current sensor and measures a current flowing througheach storage means 101. Although the first embodiment of the presentinvention has the current measuring means 103 a and 103 b and the statusdetecting means 104 separately, part or the whole of current measuringmeans 103 a and 103 b can be built in the status detecting means 104.

The status detecting means 104 mainly consists of a microcomputer and aperipheral IC and detects the status (resistances and voltages) ofrespective storage means 101 a and 101 b from the values sent from thevoltage measuring means 102 and current measuring means 103 a and 103 b.

Although the first embodiment of the present invention has the statusdetecting means 104 and the charging/discharging controlling means 105separately, part or the whole of the status detecting means 104 can bebuilt in the charging/discharging controlling means 105.

The charging/discharging controlling means 105 mainly consists of apower converter such as a converter or an inverter and controls acurrent, power, or voltage to be supplied or output to the storage means101 a and 101 b.

The currents passing through the storage means 101 a and 101 b aredependent upon their impedances Ra and Rb, their open circuit voltages(or electromotive forces) Ea and Eb, and the I/O currents, voltages, andpower of the charging/discharging controlling means 105.

Therefore, the status detecting means 104 detects the status quantitiesof the storage means 101 a and 101 b such as the impedances Ra and Rb,their open circuit voltages Ea and Eb, etc. and sends them to thecharging/discharging controlling means 105. The charging/dischargingcontrolling means 105 controls the I/O currents, voltages, and power bythe status quantities.

For example, let's assume a storage means has an impedance (internalimpedance) of R, an open circuit voltage (excluding a voltage drop dueto the internal impedance) of E, a maximum permissible voltage of Vmax,and a minimum permissible voltage of Vmin. Further, let's assume astorage means can use a permissible charging current Icmax and apermissible discharging current Idmax safely and maximally in themaximum permissible voltage range. The charging and discharging currentsIcmax and Idmax are calculated by equations (1) and (2) below.Icmax=(Vmax−E)/R  (1)Idmax=(E−Vmin)/R  (2)

where Vmax is a maximum rated voltage of the storage means or a maximumvoltage that is defined by the system such as a load connected thereto.Vmin is a minimum rated voltage of the storage means or a minimumvoltage that is defined by the system such as a load connected thereto.

FIG. 1 assumes that the open circuit voltages Ea and Eb of the storagemeans 101 a and 101 b are equal to each other as the storage means 101 aand 101 b are connected in parallel to each other and that thecharging/discharging controlling means 105 flows a current Iall tocharge and discharge the storage means 101 a and 101 b. The currents Iaand Ib which respectively flow through the storage means 101 a and 101 bcan be expressed by equations (3) and (4) where Ra and Rb are internalresistances of the storage means 101 a and 101 b.Ia=Iall×Rb/(Ra+Rb)  (3)Ib=Iall×Ra/(Ra+Rb)  (4)

Equations (3) and (4)

The charging/discharging controlling means 105 controls the current tosatisfy Expressions (5) and (6) during charging and satisfy Expressions(7) and (8) during discharging.Iall×Rb/(Ra+Rb)<(Vmax−Ea)/Ra  (5)Iall×Ra/(Ra+Rb)<(Vmax−Eb)/Rb  (6)Iall×Rb/(Ra+Rb)<(Ea−Vmin)/Ra  (7)Iall×Ra/(Ra+Rb)<(Eb−Vmin)/Rb  (8)

In other words, for charging, the charging/discharging controlling means105 controls the current to be below the less of {(Vmax−Ea)(Ra+Rb)/RaRb}and {(Vmax−Eb)(Ra+Rb)/RaRb}.

For quick charging, the charging current should be a current as high aspossible below the less of {(Vmax−Ea)(Ra+Rb)/RaRb} and{(Vmax−Eb)(Ra+Rb)/RaRb}.

Therefore, in actual current controlling, a current controlling meansshould provide a current control range considering the currentcontrolling accuracy of the means and the target charging controllingvalue should be the difference between the current control range and theless of {(Vmax−Ea)(Ra+Rb)/RaRb} and {(Vmax−Eb)(Ra+Rb)/RaRb}.

Further, the control means controls the discharging current to be belowthe less of {(Ea−Vmin)(Ra+Rb)/RaRb} and {(Eb−Vmin)(Ra+Rb)/RaRb}.

In other words, the charging/discharging controlling means 105 shouldcontrol the total current Iall by selecting the less of the maximumcurrent and the minimum current (maximum and minimum currents allowed inratings or in the system) that can flow each of the storage means 101 aand 101 b and causing the selected current to flow respectively throughthe storage means 101 a and 101 b.

Similarly, the charging/discharging controlling means 105 shouldpreferably control the discharging current efficiently to be almostequal to the maximum capacity of each storage means.

Therefore, similarly to the charging current, in actual currentcontrolling, a current controlling means should provide a currentcontrol range considering the current controlling accuracy of the meansand the target discharging controlling value should be the differencebetween the current control range and the less of{(Ea−Vmin)(Ra+Rb)/RaRb} and {(Eb−Vmin)(Ra+Rb)/RaRb}.

FIG. 2 is a functional block diagram of the inside of acharging/discharging controlling means 105.

In FIG. 2 b, the resistances Ra and Rb and the voltages Ea and Eb thatare detected by the status detecting means 104 are sent to the operationsections 105-1 to 105-3 of the charging/discharging controlling means105.

The operation section 105-1 calculates the maximum charging currents(Vmax−Ea)/Ra and (Vmax−Eb)/Rb of the storage means 101 a and 101 b. Theoperation section 105-3 calculates the maximum discharging currents(Ea−Vmin)/Ra and (Eb−Vmin)/Rb of the storage means 101 a and 101 b. Theoperation section 105-2 calculates the ratio of respective currentsflowing through the storage means 101 a and 101 b to the total current.

The operation section 105-4 calculates the maximum permissible totalcharging current Icall from Expressions (5) and (6). Similarly theoperation section 105-5 calculates the maximum permissible totaldischarging current Idall from Expressions (7) and (8).

Receiving the maximum permissible total charging current Icall and themaximum permissible total discharging current Idall from the operationsections 105-4 and 105-5, the current control section 105-6 controls thecurrent Iall that flows through the storage means 101 a and 101 b.

The current control section 105-6 comprises current control elements andmeans to switch on and off these elements to control the current Iall.

As described above, the first embodiment of this invention can safelycharge and discharge a plurality of parallel-connected storage meanswithout causing any problem. Simultaneously, this embodiment enablesquick charging, sets discharging currents effective to the capacities ofstorage means, and reduces capacities relative to the dischargingcurrents.

Although the charging/discharging controlling means 105 controlscurrents in the above example, the same effects can also be obtained bycontrolling voltages or power.

Further, although two storage means 101 a and 101 b are connected inparallel in FIG. 2, it is also possible to control the charging ordischarging currents of the storage means even when a plurality ofstorage means are connected in series and in parallel by calculatingquantities of status of each storage means such as impedances andopen-circuit voltages and expanding the above Expressions. This methodcan charge and discharge storage means safely and effectively withoutcausing any problem in the storage means instead of using a current fora single storage means as a total charging or discharging current.

When a storage means is charging or discharging, however, the voltagedetecting means detects a value including a voltage of the impedancesection, but cannot directly measure the open circuit voltage E.

It is possible to measure the open circuit voltage E and the impedance Rseparately by the following:

FIG. 3 is a graph for explaining an example of process that the statusdetecting means executes. In FIG. 3, the vertical axis (Y axis)represents voltage values and the horizontal axis (X axis) representscurrent values. This graph is for explanation only and not actuallyplotted in the status detecting means (microcomputer) 104.

The status detecting means 104 receives voltage date measured by thevoltage measuring means 102 and current data measured by the currentmeasuring means 103 for a preset time period and linearly approximatesthese kinds of data by a least-squares method.

The Y intercept of the line is equivalent to the open circuit voltage Eof the storage means 101 a or 101 b as its X value is 0. The gradient ofthe line is equivalent to the impedance R of the storage means 101 a or101 b. This approximate line is expressed by an equation Y=RI+E.

It is also possible to measure the current I and the voltage V betweenthe terminals of the storage means 101 a or 101 b, obtain theirincrements (variations) dV and dI in a very short time period, anddirectly calculates the impedance from the increments as follows:R=dV/dI  (9)

FIG. 4 is a schematic diagram of a power control apparatus which is thesecond embodiment of the invention. This embodiment is an example ofapplying the invention to a power charging/discharging controllingmeans.

In FIG. 4, a storage means 101 a and a current measuring means 103 a areconnected in series to each other. A storage means 101 b and a currentmeasuring means 103 b are connected in series to each other. A voltagemeasuring means 102 a is connected in parallel to these series sets of astorage means and a current measuring means.

Similarly, a storage means 101 c and a current measuring means 103 c areconnected in series to each other. A storage means 101 d and a currentmeasuring means 103 d are connected in series to each other. A voltagemeasuring means 102 b is connected in parallel to these series sets of astorage means and a current measuring means.

Further, these two parallel sets of a storage means and a currentmeasuring means are connected in series to another two parallel sets ofa storage means and a current measuring means. Both ends of theresulting parallel-series circuit are connected to thecharging/discharging controlling means 105. This charging/dischargingcontrolling means 105 is connected to a power supply such as acommercial power supply, a power generator and a fuel cell and to a loadsuch as an electronic apparatus (which are not shown in the drawing).

The outputs of the voltage measuring means 102 a and 102 b and thecurrent measuring means 103 a, 103 b, 103 c, and 103 d are fed to thestatus detecting means 104. The outputs of the status detecting means104 are fed to the charging/discharging controlling means 105.

In this embodiment, the status detecting means 104 is housed in thecharging/discharging controlling means 105.

The status detecting means 104 calculates the charging status (quantityof electric charge) of respective storage means 101 a to 101 d from thedetected current and voltage values and determines the maximum andminimum ones among the charging state values. The charging/dischargingcontrolling means 105 controls charging of the storage means by themaximum charging state value and discharging of the storage means by theminimum charging state value. In charging/discharging controlling, thecharging/discharging controlling means 105 controls currents, voltages,or power.

By the way, when a plurality of parallel-series connected storage meansare charged, a storage means having the greatest charging status(quantity of electric charge) completes charging first. Therefore, thecharging/discharging controlling means 105 controls charging accordingto the storage means having the greatest charging status.

Similarly, when a plurality of parallel-series connected storage meansare discharged, a storage means having the smallest charging statuscompletes discharging first. Therefore, the charging/dischargingcontrolling means 105 controls discharging according to the storagemeans having the smallest charging status.

Here, the charging status (or state of charge (SOC)) indicates how mucha storage means is charged and the discharging status (or depth ofdischarge (DOD)) indicates how much charge a storage means has todischarge.

The charging and discharging states of the storage means 101 a to 101 dcan be known from their impedances and voltage values. Further thisembodiment causes the status detecting means 104 to detect the status(such as open circuit voltage) of respective storage means 101 a to 101d and controls the charging or discharging currents according to thequantities of states in the method similar to the example of FIG. 1.Further, this embodiment controls the charging/discharging time and soon by the above charging state, that is, the greatest or smallestcharging state value.

This can provide a power storage energy management system that cancharge or discharge series-parallel connected power storage means safelywithout causing any problem.

As described above, the second embodiment of this invention canaccomplish the effects similar to those of the first embodiment andcontrol charging and discharging of respective storage means accordingto their charging or discharging status.

FIG. 5 is a schematic diagram of a power control apparatus which is thethird embodiment of the invention. This embodiment is an example ofapplying the invention to a power charging/discharging controllingmeans.

In FIG. 5, switches 106 a and 106 b are of the mechanical relay type orsemiconductor element type.

The switch 106 a is connected in series to storage means 101 a and 101 cand a current measuring means 103 c. The switch 106 b is connected inseries to storage means 101 b and 101 d and a current measuring means103 d.

These series sets of switch 106, storage means 101 and current measuringmeans 103 are connected in parallel to a charging/dischargingcontrolling means 105. A voltage measuring means 102 is connected inparallel to each storage means 101 (e.g. voltage measuring means 102 ato storage means 101 a, voltage measuring means 102 b to storage means101 b, voltage measuring means 102 b to storage means 101 b, and voltagemeasuring means 102 d to storage means 101 d).

The charging/discharging controlling means 105 is connected to a powersupply such as a commercial power supply, a power generator and a fuelcell and to a load such as an electronic apparatus (which are not shownin the drawing).

The voltage measuring means 102 a to 102 d, the current measuring means103 c, 103 d, and switches 106 a, 106 b are connected to the statusdetecting means 104 which is connected to the charging/dischargingcontrolling means 105.

The status detecting means 104 works to control and detect on/off statusof the switches 106 a and 106 b. It also detects the status values ofrespective storage means 101 a to 101 d such as internal impedances,open-circuit voltages, and charging status (remaining charges and chargequantities).

The charging/discharging controlling means 105 controlscharging/discharging currents, voltages, or powers according to theon/off status of the switches 106 a, 106 b, and the status quantities ofthe storage means 101 a to 101 d.

Switches 106 a and 106 b are used to select or replace storage meanswithout stopping the power supply. For example, you can replace eitheror both of the storage means 102 b and 102 d by new storage means bymaking the switch 106 a and opening the switch 106 b. These switches canbe used also to disconnect the storage means from a load or from thecharging/discharging controlling means 105.

Also when the storage means 101 a to 101 d are disconnected from theswitch 106 a or 106 b, the voltage measuring means 102 a to 102 d cansend the detected values normally to the status detecting means 104.

Therefore if the charging/discharging controlling means 105 charges ordischarges a storage means without knowing that a switch 106 a or 106 bis open, the storage means connected to the charging/dischargingcontrolling means 105 may be disturbed. To prevent this, the thirdembodiment of this invention detects the on/off status of the switches106 a to 106 b.

The other actions and functions of the third embodiment are similar tothose of the first embodiment.

As described above, the third embodiment of this invention canaccomplish the effects similar to those of the first embodiment evenwhen switches are connected in series to the storage means.

FIG. 6 is a schematic diagram of a power control apparatus which is thefourth embodiment of the invention. This embodiment is an example ofapplying the invention to a power charging/discharging controllingmeans.

In FIG. 6, a load 107 is a generic part such as an electronic apparatusto which a power supply apparatus supplies power.

Voltage measuring means 102 a and 102 b are respectively connected inparallel to the storage means 101 a and 101 b as shown in FIG. 6.Further, current measuring means 103 a and 103 b are respectivelyconnected in series to the storage means 101 a and 101 b.

A load 107 and a charging/discharging controlling means 105 a connectedin parallel to the storage means 101 a. Charging/discharging controllingmeans 105 a and 105 b are connected in parallel to the storage means 101b. This charging/discharging controlling means 105 b is connected to apower supply such as a commercial power supply, a power generator and afuel cell and to a load such as an electronic apparatus (which are notshown in the drawing).

Further, a status detecting means 104 a is connected to the voltagemeasuring means 102 a and a current measuring means 103 a. A statusdetecting means 104 b is connected to the voltage measuring means 102 band a current measuring means 103 b.

The status detecting means 104 a is housed in the charging/dischargingcontrolling means 105 a and the status detecting means 104 b is housedin the charging/discharging controlling means 105 b. Thecharging/discharging controlling means 105 a and 105 b are so configuredto transfer their current control signals and storage-means statusvalues to and from each other.

The purpose of this configuration is to enable the charging/dischargingmeans 101 a and 101 b to cooperate or separately work to supply power tothe load 107 or the other electronic apparatus.

The other operations and functions of the status detecting means 104 aand 104 b and the charging/discharging controlling means 105 a and 105 bare similar to those of the first embodiment of FIG. 1.

As described above, the fourth embodiment of this invention canaccomplish the effects similar to those of the first embodiment.Additionally this embodiment enables connection of multiple storagemeans and multiple charging/discharging means and enables thecharging/discharging means to share state quantity data of the storagemeans and information of respective charging/discharging means. Withthis, the power control apparatus can control charging and dischargingcurrent, voltages, or powers of the charging/discharging means accordingto the status quantities of storage means and thus utilize the storagemeans.

FIG. 7 is a schematic diagram of a power control apparatus which is thefifth embodiment of the invention. This embodiment is an example ofapplying the invention to a storage-means energy management system.

In FIG. 7, the storage-means energy management system contains acommercial power supply 108, a solar energy generator 109, power supplyswitches 110 a to 110 e, and a fuel cell apparatus 114.

A charging/discharging controlling means 105 is connected to thecommercial power supply 108, the solar energy generator 109, the fuelcell apparatus 114, and the load apparatus 107 through the power supplyswitches 110 a to 110 e.

The fuel cell apparatus 114, the solar energy generator 109, the loadapparatus 107, the power supply switches 110 a to 110 e, and the MCU ofthe charging/discharging controlling means 105 are interconnected withtwo-way communication systems. The output signals of the statusdetecting means 104 are fed to the MCU of the charging/dischargingcontrolling means 105.

The fuel cell apparatus 114 produces electric energy by oxidativereaction of oxygen (in air) and hydrogen gas stored in container orhydrogen gas obtained by modifying gasoline or methanol and outputs a.c.power through a converter or the like.

The solar energy generator 109 photo-electrically converts solar lightinto d.c. power by solar cells and outputs a.c. power through aconverter or the like.

The load apparatus 107 generically represents home electric appliances(e.g. an electric/electronic apparatus such as air conditioner,refrigerator, microwave oven, and lamps) and electric equipment (e.g.motor, elevator, personal computer, and medical apparatus).

The load apparatus 107 may contain a switch 110 in it.

The storage means 101 a to 101 d, the voltage measuring means 102 a to102 d, and the current measuring means 103 c and 103 d are connected ina configuration similar to that of the embodiment of FIG. 5 (excludingswitches 106 a and 106 b).

The MCU controls charging and discharging of the storage means 101 a to101 d by controlling a current control circuit comprising of transistors(TR1 to TR6), diodes (D1 to D6), resistors (R1 and R2), a capacitor (C),and coils (L1 and L2) according to status detection signals sent fromthe status detecting means 104 which has a function similar to that ofthe embodiment of FIG. 5.

The embodiment of FIG. 7 normally supplies required power to the loadapparatus 107 from the commercial power supply 108, the solar energygenerator 109, and the fuel cell apparatus 114.

When detecting that power from the commercial power supply 108, thesolar energy generator 109, and the fuel cell apparatus 114 is notenough, the MCU supplies power to the load apparatus 107 from thestorage means 101 a to 101 d through the charging/dischargingcontrolling means 105.

When detecting that power from the commercial power supply 108, thesolar energy generator 109, and the fuel cell apparatus 114 isexcessive, the MCU charges the storage means 101 a to 101 d through thecharging/discharging controlling means 105.

In the above operation, the status detecting means 104 detects thestatus of respective storage means 101 a to 101 d. Judging from thesestatus values, the MCU determines currents, voltages, and power requiredby the commercial power supply 108, the solar energy generator 109, thefuel cell apparatus 114, and the load apparatus 107. Thecharging/discharging controlling means 105 controls the charging ordischarging currents, voltages, and power required by them.

As described above, the fifth embodiment of this invention canaccomplish the effects similar to those of the first embodiment.

As the fifth embodiment can quickly charge storage means and obtaingreat discharging currents relative to the storage capacity withoutcausing any problem, it can reduce the contract demand and powerconsumption of the commercial power supply 108 and the rated powergeneration of the solar energy generator 109 and the fuel cell apparatus114. This can reduce charging means costs, equipment expenses, andrunning costs.

This embodiment can ease concentration of power consumption and even outthe power consumption by supplying power to the commercial power supply108 from the storage means when a power consumption concentrates on acertain period and charging the storage means when a power consumptionis less.

The energy management system for storage means stated in the fifthembodiment of this invention can take a configuration other than theillustrated one.

The fifth embodiment is applicable to production plants, buildingsystems, general households, and so on.

FIG. 8 is a schematic diagram of a power control apparatus which is thesixth embodiment of the invention. This embodiment is an example ofapplying the invention to a storage-means energy management system,particularly to railway vehicles, automobiles, and so on.

In FIG. 8, the storage-means energy management system contains alow-potential load apparatus 111, a high-potential load apparatus 112,and a motor generator 113.

The motor generator 113 is connected to a charging/dischargingcontrolling means 105 b which is functionally similar to that in thestorage-means energy management system of FIG. 7.

The storage means (101 a and 101 b), the voltage measuring means (102 aand 102 b), the current measuring means (103 a and 103 b), the statusdetecting means (104 a and 104 b), and the charging/dischargingcontrolling means 105 are configured similarly to that of FIG. 6, butthe status detecting means 104 b is not housed in thecharging/discharging controlling means 105 b.

In the embodiment of FIG. 8, the high-potential load apparatus 112 isconnected to the charging/discharging controlling means 105 b(configuration similar to that of FIG. 8) on the storage means 101 bside through the charging/discharging controlling means 105 c(configuration similar to the charging/discharging controlling means 105b). The low-potential load apparatus 111 connected to the storage means101 a.

The motor generator 113 works to start the engine (internal combustionengine), assist the driving force of the engine (powering), and generatepower (regeneration). During powering, the motor generator 113 receivespower from the storage means 101 a and 101 b. During regeneration, themotor generator 113 supplies power to the storage means 101 a and 101 b.

The low-potential load apparatus 111 are electric loads and other powersupply units of rated voltages from some volts to 42 volts such assolenoid valves of the engine and audio sets.

The high-potential load apparatus 112 are electric loads having ratedvoltages of some hundred volts such as lamps and an air conditioner.

Also in this embodiment, the status detecting means 104 a and 104 bdetect the status of respective storage means 101 a and 101 b. Thecharging/discharging controlling means 105 b controls charging ordischarging currents, voltages, and powers according to the detectedstatus quantities considering the I/O requests of the motor generator113, the low-potential load apparatus 111, and the high-potential loadapparatus 112.

This embodiment enables the charging/discharging means (105 a to 105 c)to share state quantity data of the storage means (101 a, 101 b and 101c) and information of respective charging/discharging means (105 a, 105b, and 105 c) and thus utilizes the storage means.

As described above, the sixth embodiment of this invention canaccomplish the effects similar to those of the first embodiment.

When applied to a tracked vehicle such as electric car, hybrid electriccar, railway car, and mono-rail car, the power storage energy managementsystem which is the sixth embodiment of this invention can reduce thecharging time and the weight of the storage means. Therefore, thissystem can assist engine torques at the startup of the engine, convertkinetic energy of braking into electric power, and store the regeneratedpower, which leads to reduction of shipping cost of the system andmaintenance frequency.

Although the above embodiment is an example of applying a power controlapparatus of this invention to a charging/discharging controlling means,this invention can also be applied to a charging controlling apparatusand a discharging controlling apparatus.

In other words, when applied to a charging controlling apparatus, thepower control apparatus calculates the internal impedance of eachstorage means from the detected current and voltage and controls thecharging current to satisfy Expressions (5) and (6).

When applied to a discharging controlling apparatus, the power controlapparatus calculates the internal impedance of each storage means fromthe detected current and voltage and controls the discharging current tosatisfy Expressions (7) and (8).

Further, as the embodiments of this invention can calculate the internalimpedance of respective storage means, it is possible to estimate theservice life of each storage means from its impedance value. Thisestimation is carried out by the current controlling section 105 f inFIG. 2.

Therefore, it is possible to show the service life and the expectedreplacement time of each storage means.

This invention can provide a power control apparatus that can controlcharging and discharging of a plurality of storage means without causingany problem while reducing the charging periods and capacities relativeto the discharging current values.

Although the present invention has been illustrated and described withrespect to exemplary embodiment thereof, it should be understood bythose skilled in the art that the foregoing and various other changes,omission and additions may be made therein and thereto, withoutdeparting from the spirit and scope of the present invention. Therefore,the present invention should not be understood as limited to thespecific embodiment set out above but to include all possibleembodiments which can be embodied within a scope encompassed andequivalent thereof with respect to the feature set out in the appendedclaims.

1. A tracked vehicle having a motor generator which assists the drivingforce of the engine, a plurality of storage means, and a power controlapparatus which controls charging and discharging of said plurality ofstorage means; wherein said power control apparatus comprises: a voltagemeasuring means for measuring voltages of each of said storage means; acurrent measuring means for measuring currents flowing through each ofsaid storage means; a status detecting means for detecting an operatingstatus of each storage means, from values measured by said voltagemeasuring and current measuring means; and a charging/dischargingcontrolling means for controlling one of currents, voltages, and poweraccording to said operating status of each storage means, to charge ordischarge said storage means; wherein, said status detecting meanscalculates one of an internal impedance and open circuit voltage of eachstorage means; and said charging/discharging controlling meanscalculates a permissible charging or discharging current value of eachstorage means from its internal impedance, open circuit voltage, presetmaximum permissible voltage and minimum permissible voltage, calculatesa sum of all currents flowing through said storage means to suppress acurrent over the calculated permissible charging or discharging currentfrom flowing into or out of each of said storage means, and controls thecharging or discharging current to maintain the total current below thecalculated total current value.
 2. A tracked vehicle according to claim1, wherein said power control apparatus shows the service life and anexpected replacement time of said each storage means calculated fromsaid impedance of said each storage means.
 3. A tracked vehicleaccording to claim 1, wherein said storage means is one of a lithiumsecondary cell, a nickel metal-hydride battery, a lead-acid battery andan electric double layer capacitor.
 4. A tracked vehicle according toclaim 1, wherein said motor generator is operable to start the engine,assist the driving force of the engine or generate power.
 5. A trackedvehicle according to claim 1, wherein said tracked vehicle is a railwaycar or a monorail car.